Robots to the Moon
exposure. These shots are radioed to a NASA
installation at Goldstone, California, 120 miles
northeast of Los Angeles in the Mojave Des
ert (opposite). As Ranger flies ever nearer, it
makes more than 150 lunar close-ups, each
picture covering a smaller area than the one
before, with increasingly better definition.
When Ranger's radar altimeter senses that
it is 70,000 feet above the moon, it figurative
ly shouts, "Land ho!" The photographic mis
sion is ended; Ranger is about to come apart
and prepare for landing.
Retrorocket Brakes the Capsule
Now the lunar capsule begins its useful life.
The outer shell of this 24 1/2-inch ball is wood
- balsa, six inches thick, light, springy, and
tough. Inside the balsa are a variety of things:
a moonquake sensor, a radio transmitter, two
guns, three pints of water, half a pint of vol
atile heptane.
At the altimeter's signal, the lunar capsule
is detached from the $6,000,000 basic bus,
which tumbles full speed into the moon. A
small retrorocket slows the lunar capsule to
a dead stop some 1,100 feet above the surface
(page 563). Then the rocket drops off, and the
lunar capsule, sucked in by the moon's grav
ity, hits the bleak landscape, bounces, and
rolls to a stop. It lands silently (there is no
noise on the moon, because there is no air to
carry sound waves). The only damage is a
crushing of the balsa on one side (page 564).
The balsa ball may have landed so that the
instruments it contains are upside down, and
this has been provided for. Inside the balsa
shell nest two concentric Fiberglas spheres
separated by one-tenth of an inch of liquid
Freon. The inner sphere, holding the instru
ments, is weighted at the bottom. It rotates
in the liquid by the force of gravity until the
instruments are right side up and the anten
na points toward earth and the listeners at
Goldstone.
For at least a thousand million years, prob
ably far longer, nothing has landed here but
lifeless chunks of rock or metal, including an
inert Russian probe and the dead Ranger 4.
But today something happens that, so far as
we know, has never occurred on the moon.
This intruder moves, moves of its own ac
cord. It is a small movement, granted, and
only a by-product of clearing the lunar cap
sule's interior for action. Two guns go off in
side, and the capsule shudders as the bullets
pierce the Fiberglas spheres and the balsa.
The Freon spurts out the holes, instantly va
porizing in the lunar vacuum, and so does the
heptane that fills the moonquake sensor, or
seismometer, to protect its moving parts dur
ing the rough landing. The capsule is now
"frozen" in its working position.
This modern Santa Maria, which has been
in its new world 20 minutes, is now ready to
report to its masters. If the moonquake sen
sor jiggles, radio signals flash the fact to earth
in less than two seconds.
Ranger's seismometer can feel the shock of
a five-pound meteorite hitting the other side
of the moon. At Goldstone, I saw a Ranger
seismometer that had been dropped in its
capsule from an airplane over the Mojave
Desert in a test of its ruggedness. It survived,
and remained so sensitive that it recorded the
air motion of a piece of typing paper waved
two feet away.
Walter Larkin, engineer in charge at Gold
stone, said: "We had this set up once in a
room with the door closed. Just by watching
its reactions, we could tell when a girl was
walking down the corridor-and we could
tell the plump ones from the slim ones."
Instruments Survive Heat and Cold
The great problem on the moon's surface is
the extreme heat and cold. During the lunar
day, when the sun beats down, the moon's
surface reaches 248° Fahrenheit. In the lunar
night, the surface cools rapidly to minus 238°.
The instruments could not work at all in these
extremes, were it not for the temperature
controlling water in the capsule's tanks.
In daytime, the predominantly white color
of the sphere will, by reflecting sunlight, hold
down the internal temperature. The balsa
wood and insulation inside the capsule will
also help. Most important, however, is the
water, which will temper the interior "cli
mate" as oceans do the seacoasts. When tem
peratures rise too high, some of the water will
boil off through a poppet valve, cooling the
instruments by evaporation.
At night, the water will eventually freeze.
But by the time the ice gets much below 32°,
sunlight will be warming the capsule again.
In about 30 days, all the water will have
evaporated, and the signals will stop.
Why should our first lunar instrument be a
seismometer? Because it can tell us much not
only about the moon, but also about the earth
and the formation of the solar system.
First, it can define the hazard that a human
569